1. Population Research Unit; Department of Social Research; University of Helsinki; Helsinki; Finland
2. Max Planck Research Group Lifecourse Dynamics and Demographic Change; Max Planck Institute for Demographic Research; Rostock; Germany
3. Child and Adolescent Public Health Epidemiology; Department of Public Health Sciences; Karolinska Institutet; Stockholm; Sweden
4. Department of Community Health Nursing; Osaka City University; Osaka; Japan